1. Field of the Invention
The present invention relates to a method and an apparatus for controlling a wireless communication system. More particularly, the present invention relates to a method and an apparatus for resource allocation scheduling in a wireless communication system.
2. Description of the Related Art
The Institute of Electrical and Electronics Engineers (IEEE) 802.16e-based communication system is a system employing an Orthogonal Frequency Division Multiple Access (OFDMA) scheme in order to support a broadband transmission.
The IEEE 802.16e-based communication system channels multiple subcarriers among all subcarriers having orthogonality and forms sub-channels. Further, in the IEEE 802.16e-based communication system, data transmission is performed frame by frame, and sub-channels during a specific symbol duration within a single frame are combined to generate a slot, which is a minimum unit having two-dimensional resources of time and frequency.
A downlink sub frame included in a single frame includes a DownLink (DL)-MAP region and an UpLink (UL)-MAP region. The base station includes DL data burst allocation information and UL data burst allocation information of a mobile station to the DL-MAP region and the UL-MAP region, respectively, so that the corresponding data burst can be transmitted in the DL and UL data areas by using the multiple slots.
Hereinafter, a structure of a frame in a conventional wireless communication system will be described with reference to FIG. 1.
FIG. 1 is a view illustrating a structure of a frame in a wireless communication system according to the related art.
Referring to FIG. 1, the frame includes a DL sub-frame 100 and a UL sub-frame 150.
The DL sub-frame 100 includes a preamble region 110, a DL-MAP region 120, a UL-MAP region 130, and a DL burst region 140. The UL sub-frame 150 includes a UL burst region 160.
The preamble region 110 is used in order to transmit a preamble signal for acquisition of synchronization between a base station and a mobile station.
The DL-MAP region 120 and the UL-MAP region 130 are used for transmission of a DL-MAP message and a UL-MAP message, respectively. The DL-MAP message and the UL-MAP message include information indicating whether a DL burst region and a UL burst region are allocated to each of the mobile stations, and location information of the allocated DL burst region and UL burst region and modulation scheme information used when the DL burst region and the UL burst region have been allocated to each of the mobile stations.
The DL burst region 140 is used for transmission of a DL data burst and the UL burst region 160 is used for transmission of a UL data burst.
The UL-MAP message is transmitted through the DL sub-frame 100, so that the base station generally first performs a UL scheduling for scheduling of an allocation order of UL resources prior to DL scheduling for scheduling of an allocation order of DL resources.
FIG. 2 is a diagram illustrating a structure of a frame after the performance of UL scheduling according to the related art.
Referring to FIG. 2, when the UL scheduling is performed, a remaining region 230, other than a preamble region 210 and a UL-MAP region 220, exists in a DL sub-frame 200. Therefore, after the performance of the UL scheduling, the allocation of the DL data burst is determined in accordance with a size of the remaining region 230.
When a size of the remaining region 230 is larger than a size of the DL data burst to be allocated, there is no problem regarding the allocation of the DL data burst to the remaining region 230. However, in the alternative case in which the size of the DL data burst to be allocated is larger than a size of the remaining region 230, the DL data burst can still be allocated to the remaining region 230 depending on whether the DL data burst can be fragmentized.
Specifically, the DL data burst, which can be fragmentized, can be fragmentized and allocated to the remaining region 230, to be transmitted. However, if the size of the remaining region 230 is smaller than that of a DL data burst that cannot be fragmentized, such as a Medium Access Control (MAC) management message and Hybrid Automatic Repeat Request (HARQ) retransmission traffic, then a problem occurs in that it is impossible to allocate the DL data burst to the remaining region 230. Therefore, there occurs a problem in that the DL data burst that cannot be allocated cannot be transmitted.
As an example, a mobile station located at an edge of a cell uses a Modulation and Coding Scheme (MCS) level relatively lower than that used in another mobile station within the cell, so that when the UL-MAP is first allocated to the DL sub frame, a space for the allocation of the DL data burst is lacking, so that there may occur a problem of the transmission interruption of the DL data burst. This is because the mobile station located in the edge of the cell requires a relatively large DL burst region in comparison with the other mobile station.
A size of the DL data burst to be transmitted is determined according to a size of an Automatic Repeat Request (ARQ) block. Therefore, in order to address the above problem, there may be conceived a solution of reducing a size of the ARQ block, but the number of ARQ blocks, which can be transmitted one time, are limited according to an ARQ window size. Therefore, in the event of reducing the size of the ARQ block, there occurs a problem of a decrease in throughput according to the transmission/reception of the data burst.
Further, a UL signaling message or a DL MAC management message including a Basic-Connection Identifier (B-CID) and a Physical-Connection Identifier (P-CID) is a sequentially transmitted message, so that in the event of the transmission interruption, all of the subsequent UL signaling message or DL MAC management message cannot be transmitted for several frames according to a size of a UL-MAP region. In this respect, there occurs a problem in deterioration of a success rate of a handover or Quick Connection Setup (QCS) of the mobile station. Likewise, when the transmission of a broadcast MAC management message related to an operation of a system is interrupted, there occurs a serious situation of the failure of the operation of the system.
Accordingly, there is a need for an improved method and an apparatus for resource allocation scheduling in a wireless communication system.